The IEEE P802.3bq Task Force is currently working on a standard for 40GBASE-T. This standard includes requirements for a wide variety of parameters such as requirements for the PHY to PHY link 100 shown in FIG. 1. A PHY refers to a semiconductor chip in equipment, such as switch, which interfaces to the physical layer, and which transmits and receives data sent over a channel. This PHY to PHY link 100 includes the structured cabling 101 with elements such as a jack 102, horizontal cable 104, and patch cords 106. It also includes elements on the equipment 107 like a medium dependent interface (MDI or jack on the equipment) 108, magnetics on the equipment 110, and circuit board equipment traces 112 connecting the MDI to the magnetics and PHY chip 114. The overall performance of this PHY to PHY link 100 may be critical as better performance in this PHY to PHY link 100 implies that the PHY semiconductor chip 114 consumes less power and is be easier to design and manufacture, minimizing the time to market and maximizing the broad market potential.
The overall PHY to PHY channel performance for parameters like return loss and NEXT is essentially a summation of the structured cabling 101 and the elements on the equipment 107. Whatever PHY to PHY element has the worst performance generally dominates the overall channel performance and make improvements to any other element meaningless. The weakest point in a channel is may be magnetics 110, such as isolation transformers or other similar devices. Magnetics 110 provide port isolation but can cause parameters like return loss to be excessively high.
If it is decided to improve the performance or remove the magnetics, a limiting factor in the channel performance may be the structured cabling channel 101. Currently there are at least two approaches: an RJ45 path using F/UTP cabling and a switchable RJ45 path using S/FTP cabling. U.S. patent application Ser. Nos. 13/864,924 and 61/889,723, both of which are herein incorporated by reference in their entirety, show an ARJ45 plug design and a switchable jack design, respectively.
However, if equipment vendors decide to not adopt a switchable connector for the MDI 108 due to reliability or cost concerns, they may choose to adopt the simpler ARJ45 connector which offers the same benefit in performance without the backwards compatibility to RJ45. This may or may not present a compatibility concern depending on how the copper structure cabling solution is deployed.
Switchable RJ45 jacks can work well under a 40GBASE-T End of Row deployment. In this deployment scenario, copper is used to connect servers to a 40GBASE-T access switch. This can be done through switchable RJ45 switch cabinet jacks, horizontal cable, switchable RJ45 server cabinet jacks, and patch cords. In this case, if the servers are 10GBASE-T servers with RJ45 jacks, they can interface to the 40GBASE-T access switch by using Category 6A patch cords as patch cords. If the servers are upgraded to 40GBASE-T with ARJ45 jacks, then it is only necessary to switch patch cords to ARJ45 patch cords.
A Top of Rack deployment is becoming increasingly common within today's data centers, and is a likely deployment scenario for 40GBASE-T. The switchable RJ45 jack may not provide any benefit under a 40GBASE-T Top of Rack deployment. In the case of a Top of Rack deployment, copper patch cords may be used to directly connect servers to a fabric extender (which also can be an access switch). If a 40GBASE-T switch with an ARJ45 jack needs to interface with a 10GBASE-T server with an RJ45 jack, a hybrid patch cord is required with an ARJ45 plug on one end and a RJ45 plug on another end.
Many data center managers do not like having to maintain this extra hybrid patch cord inventory. There are also some concepts that suggest putting a switching RJ45 on the equipment as the MDI which can interface to both RJ45 plugs and ARJ45 plugs; however, this requires support for the MDI manufacturers. These MDI manufacturers may be cost sensitive and reluctant to invest in tooling for a complicated switching jack for which they may have low profit margins.
Therefore, it may be desirable to connect a non-switching ARJ45 jack on switch equipment with a 10GBASE-T port on a server, or other end equipment, using Category 6A RJ45 to RJ45 patch cords.